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Author Topic:   Carburetor
posted January 21, 2004 03:25 PM
They have changed the rules on me and now allow any carb. I have a 750 holley on the shelf, but it has vaccum secondaries. Has anyone tried a vaccum secondary on a dirt track.

posted January 21, 2004 03:39 PM
I use a Holley HP series vac. 750 and love it. Super smooth on dry, responsive on tacky.

posted January 22, 2004 10:33 PM
We're limited to the Holley 3310 vac sec 750. More than likely that's what you have. We can't add a secondary metering plate, but if you can go for it. It's much easier to change jets than drill the secondary plate. Also get a $10 quick change spring kit and a set of springs. Try the purple spring first, and if it doesn't bog, go for the yellow one. With stock jetting, the yellow might work. I drilled the secondary plate to be approx. 78 or 80 jets. Works perfect with the purple spring.

If it bogs, the springs to light. If it wheezes at half track, the springs to tight. Go with the lightest spring you can and not have a bog. Personally, I think it's easier to tune in a vac. carb than a mechanical. The engine does the tuning for you.

posted January 26, 2004 11:24 AM
My class is required to run dual-line, vacuum-secondaries, with no removal of the choke horn. I agree with tilley88 about the 750 cfm HP Holley. I believe the part number is 80529, and it has no choke tower to begin with, so I got through tech (barely) one night on that one! I sure hope they don't outlaw it this year, because it's a great carb. It's expensive, though. Over $600 I think.

posted January 26, 2004 06:20 PM
How does the vacume secondary work when your getting off the throttle going in to the turn. Does it shut down as quick as the mech. secondarys. I've been thinking of trying one of these but thats the one thing I was wondering about.

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